Optical proximity sensor

Abstract

An optical proximity sensor includes an infrared light emitter, a light detector, and an integrator circuit. The infrared light emitter is configured to emit AC pulses of infrared light, and emit no or low levels of infrared light in-between AC pulses. The light detector is configured to detect ambient light DC signals and infrared light AC pulses emitted by the light emitter and reflected from an object to be detected towards the light detector. The integrator circuit performs a proximity measurement employing the light emitter and the light detector. The integrator circuit includes an ambient light measurement circuit configured to perform an ambient light measurement before performing a proximity measurement and to configure measurement settings of the light emitter and/or the light detector and/or the integrator circuit based on the ambient light measurement. The integrator circuit is configured to perform the proximity measurement based on the measurement settings.

1 . An optical proximity sensor, comprising:
 an infrared light emitter configured to emit AC pulses of infrared light, the infrared light emitter further being configured to emit no or low levels of infrared light in-between AC pulses;   a light detector configured to detect ambient light DC signals and infrared light AC pulses emitted by the light emitter and reflected from an object to be detected towards the light detector, and   an integrator circuit which performs a proximity measurement employing said light emitter and said light detector,   
       wherein 
       said integrator circuit comprises an ambient light measurement circuit configured to perform an ambient light measurement before performing a proximity measurement and to configure measurement settings of said light emitter and/or said light detector and/or said integrator circuit based on said ambient light measurement, and wherein said integrator circuit is configured to perform said proximity measurement based on said measurement settings. 
     
     
         2 . The optical proximity sensor according to  claim 1 , wherein said integrator circuit is configured to perform proximity measurements in cycles, and whereby said ambient light measurement circuit is configured to perform an ambient light measurement at the begin of each cycle. 
     
     
         3 . The optical proximity sensor according to  claim 1 , whereby said measurement settings are configured based the measured ambient light intensity. 
     
     
         4 . The optical proximity sensor according to  claim 3 , whereby a plurality of ambient light intensity ranges is defined, and whereby for each intensity range related measurement settings are defined in said integrator circuit, and whereby said integrator circuit is configured to select said related measurement settings based on the intensity range which comprises the measured ambient light intensity. 
     
     
         5 . The optical proximity sensor according to  claim 3 , whereby as a measurement setting the power of said light emitter during said proximity measurement is set dependent on the ambient light intensity. 
     
     
         6 . The optical proximity sensor according to one of the  claim 3 , whereby as at least one measurement setting at least one parameter of said light detector is set dependent on the ambient light intensity. 
     
     
         7 . The optical proximity sensor according to one of the  claim 3 , whereby as a measurement setting the amplification factor of said integrator circuit is set dependent on the ambient light intensity. 
     
     
         8 . The optical proximity sensor according to  claim 7 , whereby said integrator circuit comprises an operational amplifier and a capacitor arrangement with a plurality of capacitors that can be arranged electrically parallel to said operational amplifier, and whereby said integrator circuit is configured to select a parallel capacitor of said capacitor arrangement depending on said measured ambient light intensity during said proximity measurement. 
     
     
         9 . The optical proximity sensor according to  claim 1 , whereby said an ambient light measurement circuit is identical to said integrator circuit. 
     
     
         10 . The optical proximity sensor according to  claim 1 , comprising a crosstalk measurement circuit. 
     
     
         11 . The optical proximity sensor according to  claim 10 , comprising an ADC, whereby the outputs of said measured ambient light and said cross talk measurements are converted to digital signals in said ADC, and whereby a digital core is configured to conduct ambient light and cross talk corrections of the digitized proximity measurement signal. 
     
     
         12 . The optical proximity sensor according to  claim 10 , whereby in crosstalk calibration coefficients are stored in a digital core which are applied during crosstalk correction based on the measured crosstalk signal. 
     
     
         13 . The optical proximity sensor according to  claim 1 , which is configured to provide normalized proximity data as an output. 
     
     
         14 . The optical proximity sensor according to  claim 1 , whereby said light detector is built as a photo diode. 
     
     
         15 . A method for detecting the proximity of an object, comprising the steps of:
 in an integrator circuit conducting a proximity measurement by emitting AC infrared radiation by an infrared emitter and measuring the reflected radiation by a light detector; and   conducting an ambient light measurement,   
       wherein 
       said ambient light measurement is conducted before said proximity measurement, and said infrared emitter and/or said light detector and/or said integrator circuit are configured for said proximity measurement based on said ambient light measurement.